Electronic switching system



Filed Feb. 25. 1945 Patented Dec. 28, 1948 UNITED STATES PATENT OFFICE ELECTRONIC SWITCHING SYSTEM J ohn H. Newitt, Montclair, N. J., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application February 23, 1945, Serial N0. 579,451

4 Claims. (Cl. 343-121) The present invention relates to electronic switching systems especially adaptedv for switching ultra-high frequency currents, and particularly to that type of switching in which the current is abruptly switched from completely oil to completely on, or vice versa.

In certain applications of switching systems. it is important that the current be abruptly switched, that is, abruptly turned on or "om" For example, in several types of direction finders and radio beacons, particularly of the amplitude comparison type, switching systems are employed as goniometers to shift' the radiant action patterns of the antenna system. One such direction finding system lis illustrated and described in the co-pending application of Nathan Marchand, for Direction finders, :tiled November 25, 1944,

bearing Serial Number 565,142, now Patent No.

the foregoing will be best understood from the following description of an embodiment thereof. reference being had to the accompanying drawing in which:

Fig. 1 is a diagram, partly schematic and partly in block form, of a direction ilnding system including an electronic switching system embodying my invention;

Fig. 2 is a detailed cross-sectional view, partially in elevation, of one of the electronic discharge devices of the electronic switching system showing the ground connection forthe grid; and

be completely switched oil', even though electronic iiow is blocked, due to the interelectrode capacities. Because of these diillculties, the tendency of the' art has been towards transmission line or capacitive switching at these ultra-high frequencies despite the superior convenience and other advantages of electronic switching.

An object of the present invention is the provision of an improved electronic switching system which is suitable for, abruptly switching completely on and off current of ultra-high frequencies, such as about 100 to 600 megacycles or over.

Another object of the present invention is the provision of an improved shiftable radiant acting system for ultra-high frequency currents utilizing electronic switching of the typeherein described.

A still further object of the present invention is the provision of a direction nding system for ultra-high frequency current in which electronic switching `of the type described is used to shift the radiant action pattern.

Other andfurther objects and advantages of the present invention will become apparent and Fig. 3 is a set of curves used to describe the relationship of the switching control voltages of, the electronic switching system of Fig. 1.' f

As shown in Fig. 1, I provide four antenna units l, 2, 3 and 4, each of which is rendered unidirectional by shield means 5, E, 'l and 8 respectively. The antenna units illustrated are dipoles and are respectively connected by dual transmission lines 9-I2 respectively to known conversion boxes |3'-I 6y respectively. These conversion boxes convert from the balanced dual-transmission lines to coaxial lines I1-20 respectively.

Coaxia1 lines I`I--20 are sequentially coupled` by means of an electronic switching system 2l to a direction ndlng receiver 22 which has at its output an indicator 23.

Electronic switching system 2| is comprised of four electronic switches 24-21 which are adapted to sequentially couple antennas i-4 respectively to the direction ilnding receiver 22. Since all of said switches are .similar in construction a description of one of said switches will suillce.

Switch 24 includes an electron discharge device or tube 28. Since the electronic switch 24 is adapted to operate vover a relatively wide band of frequencies and in the range of about 100-600 megacycles or overalthough of course it will be appreciated that this switch may also be used at lower frequencies-a special type of tube in a special arrangement is required.

Tubes satisfactory for use in electronic switch 24 are characterized by the fact that the transit angle is small at the operating frequency, which requires close spacing between the electrodes, and are characterized further by the fact that the anode and its leads are completely shielded from the cathode and its leads by the grid and the grid connector or grid lead. Among types of tubes satisfactory for this purpose are those commercially known as lighthouse tubes" and various forms of disk seal tubes.

Referring now to Fig. 2, I have there illustrated a known form of lighthouse tube. .Tube 2l is a triode having an anode 29, a grid 99 and a cathode 3i heated by a heater 32. The electrodes 29- ji/are provided respectively with low inductance and low impedance leads 33-95. Leads 99 and 34 are in the form of disks. The grid lead or grid disk 34 extends through the walls of the tube envelope :itA alongallhradii. Grid .disk 3 4 has an openingv therein across' which the grid 30 extends, said grid and disk both being flat and substantially coplanar and'serving as, an electrostatic shield shielding the anode and its leads from the cathode and its leads. It will therefore be seen that the grid forms an unbroken continuous shield across the opening of the grid disk 34. Since the grid is flat. the active surfaces of the anode 29 and cathode 3i may be arranged immediately adjacent thereto therebyproviding a short transit time.

In accordance with my invention, the grid 301s maintained at ground potential for radio .frequency. I accomplish lthis by arranging a flat conductor 91 againstthe upper surface of the grid disk 34, which conductor 91 is separated by Aa thin insulating member 39. such as a thin sheet of mica, from a conductive surface-39 serving as ground. The surface 99 may be the chassis or frame of the electronic switching sys" tem 2l or any similar conductive surface maintained at ground potential. The dimensions of this condenser arrangement :49, shculdl be so chosen that the grid is maintained at ground potential at the operating frequency. Said arrangement provides a non-inductive ground connection which will offer' substantially no impedance to radio frequency current and conse# quently maintain the gridat ground potential. Of course it is to' 'be understood that the conductive member 31 might beomittcd and the grid disk 34 serveas one plate of the condenser.

The radio frequency energy from antenna I, transmitted over coax'ialline. i1, is -impressed upon the cathode 3i of tube 28. the inner conductor 4| of said coaxial line being' coupled to the cathode with the-outer conductor thereof being coupled to ground.4 The cathode resistor 42 also serves asthe matching' terminating impedance of line '|7. Through an .isolating circuit 49, switching control voltages from a source 44 are are two general vmodes of operation. In the first-mode of operation, the tubes are normally blocked and the source 44 supplies positive pulses to unblock the tubes sequentially. In a second form of operation, the tubes are normally conductive and the source of switching control voltages supplies blocking voltages to three of the fourtubes at a time to block all but one of said tubes, the one of said tubes that is unblocked being changed sequentially. This latter mode of operation will now be described in connection with Fig. 3. Y

The tubes of the electronic switches 24-21 are normally biased so that said tubes are nonconductive. This biasing voltage may be supplied in series with the source 44 or as a part thereof with the blocking switching control voltages superimposed on the normal bias which latter renders the tubes conductive.

The four curves of Fig. 3 show the switching control voltages applied to the lines 45'-4 from source 44. The pulses illustrated in said curves are negative and are adapted to abruptly block thev tube to which they are applied. Inbetween said pulses the tubes are conductive.l Consequently it will be seen that between time To and Ti the tube of switch 24, between. time Ti and T2, the tube of switch 29, between time Ta and Ts the tube of 'switch 29, and between time Ta and T4 the tube of switch 21, will alone be conductive. Thus it will be seen that the switches are sequentially operated.

If, however, it is desired to have the tubes normally' blocked, the positive pulses are applied for periods from Tn to T1 to render switch 24 operative and for like short periods T1 to T2 for switch 25, T2 to T3 for switch V26, and T3 to T4 for switch 21. In this mode of operation only one tube at a time is conductive and the tubes become conductive sequentially.

While I have described my invention in connection with a direction finding system,` it is ,obvious that it may not only be employed with transmitted over "line 45 to the grid' I of tube 28 of 'switch 24. Similarly switching control voltages are suppliedl from said source 44 and over similar lines 46, 41 and 49` 'to the grid of the tube in switches'25, 2c and 21 respectively. The anodes of the tubes in saidl switches are coupled'together and to` 'the direction finding-receiver 22. They are also connected in series with a tunable resonant circuit inthe form' of an adjustable resonantllne 49 through an' isolation network 50 to a source of positive potential B+. Line 49 may be tunedto the"frequency at which the system is operating by means of a tuner 5I. adjusting the point at which the-inner conductor 52 is grounded at radio frequency capacitively. Other forms of, Atuning may, of course, be employed as well as other forms of resonant sections.

The operation of switches 24-21 is controlled by the conduction of their tubes. Said .tubes are adapted to l'become conductive in sequence and this is controlled by the voltages derived from the source of` switching voltages, Since the tubes are to be switched abruptly on and oi, the source 44 supplies ,-'rectangular pulses as illustrated in Fig. 3 to th'e various lilies .4l-4l associated with the respective circuits. Theftother shiftable radiant acting vsystems but in many other uses. Furthermore, it is clear that modifications of the electronic switching system disclosed will occur to those skilled in the art. Therefore it should be distinctly understood that this description is given merely by way of illustration and is not to be considered a limitation on my inventionv as indicated inthe objects thereof and defined in the accompanying claims.

I claim:

1. An electronic switch system for switching current from an ultra high radio frequency source to a load comprising an electron discharge device having an envelope, an anode, a cathode, leads for the cathode yand anode. a grid, and a low impedancegrid lead providing an external terminal for the grid and connected inside -the envelope thereto, said grid le'ad and grid serving as an electrostatic shield between the anode and its lead and the cathode and its lead, means forming a substantially non-inductive capacity coupling said grid lead to ground and of such a value as =to maintain said grid at ground poten- -tial for the radio frequency current to isolate said anode and said cathode, an impedance means coupling said cathode to ground, means for coupling .said source across said impedance means, a

.source of switching control voltages. means im- .pressing said switching control voltages on saidv grid, and means coupling the anode to said load.

frequency sources to'a load including a plurality of electronic switches; each of said switches comprising an electron discharge device having an envelope, an anode, a cathode, leads for the cathode and anode, a grid, and a low impedance grid lead providing an external terminal for the grid and yconnected inside the envelope thereto, said grid lead and grid serving as an electrostatic shield between the anode and its lead and the cathode and its lead, means forming a substantially non-inductive capacity coupling said grid lead to ground and of such a value as to maintain said grid at ground potential for the ultra high radio frequency current to isolate said anode and said cathode, an impedance' means coupling said cathode to ground, means for -coupling one of said sources across said impedance means; a

source of switching control voltages; means impressing said switching control voltages on the grid of a given number of said switches in a, given sequence; and means coupling the anodes of said devices to said load.

3. A shiftable radiant acting system comprising a plurality of differently directed antennas; a translating device; and an electronic switching system for switching current from said antennas to said translating device, said electronic switching system including a, plurality," of electronic switches each comprising an electron discharge device having an envelope, an anode, a cathode, leads for the cathode and anode, a grid, and a low impedance grid lead providing an external terminal for lthe grid and connected inside the envelope thereto, said grid lead and grid serving as an electrostatic shield between the anode and its lead and the cathode and its lead, means forming a substantially non-inductive capacity coupling said grid lead to ground and of such a given sequence; and means coupling the anodes of said electron discharge devices to said translating device.

4. A direction finding system comprising a p1urality of differently directed antennas; a direction finding receiver; and an electronic switching system for switching current from said antennas to said receiver including a plurality of'electronic switches each comprising an electron discharge device having an envelope, an anode, a cathode. leads for the cathode and anode, a grid, a grid lead providing an external terminal for the grid and connected inside the envelope thereto, said grid lead land grid serving las an electrostatic shield between the anode and its lead and the cathode and its lead, means forming a substantially non-inductivecapacity coupling said grid ieadto ground and of such a value as to maintain said grid at'ground potential for the ultra high radio frequency current to isolate said anode and said cathode, an impedance means coupling said cathode to ground, andmeans for coupling one of said antennas across said impedance; a source of switching control voltages; means im' pressing said switching control voltages on the grid of a given number of said electron discharge devices in a given sequence; and means coupling the anodes of said electron discharge devices to said direction flnding receiver.

l JOHN H. NEWI'IT.

REFERENCES CITED The following references are of record in the ille of this patent: 

